Although reliable associations have been established among a wide variety of social and biological precursors and risky, illegal, or psychopathological behavior in adolescence, the epidemiological and etiological details of how these factors combine remain to be understood in detail. Several extraordinarily detailed datasets are currently available, encompassing multiple cohorts, cultures and ethnicities. We propose to make use of unique and untapped potential in four existing datasets: The Australian Twin Registry, The Virginia 30,000, Add Health, and the Nonshared Environment and Adolescent Development project. Although the datasets all contain variables relevant to the explanation of disrupted development in adolescence, they have been collected with different emphases, ranging from the social and psychological to biological and genetic. The central theme of the current application is that family data, encompassing biological and social relations among parents and children, siblings, and twins, provides a unique window on the complex interplay of biological and social factors that combine in adolescent development. The application describes an integrated program of research combining the methodological and substantive expertise of a core group of investigators in behavioral genetics, developmental psychopathology, and social development in families. Throughout, our goal is to extend the limits of developmental social science in adolescence by employing genetically informative family data, while extending the scope of developmental behavioral genetics by getting beyond traditional variance partitioning approaches, applying genetically informative methods to the testing of specific questions about causal relations in complex developmental systems. Public Health Relevance: It is well-known that many aspects of family functioning and social environments like neighborhoods are associated with disrupted behavior in adolescence. In addition, there is a clear body of evidence demonstrating associations between biological characteristics of children and disrupted behavior. Both social and biological associations with problem behaviors in adolescence, however, can occur for at least two kinds of reasons, and it is crucial to be able to tell them apart. On the one hand it may be that the social or biological predictors actually cause the disrupted behavior;on the other hand, it could also turn out that the predictors are associated with the outcomes because of other factors. For example, if impoverished families provide less supervision to their children, and poverty also causes the children to be more likely to act out, lower supervision will be associated with acting out even though it does not cause it directly.